The present invention relates to a toroidal type continuously variable transmission (CVT), and more specifically to a toroidal transmission having two toroidal cavities around a common axis (often called a dual cavity type).
Japanese Patent Provisional Publication No. 62-258255 discloses one conventional example. A toroidal transmission of this example has a first toroidal cavity formed between input and output discs of a first toroidal transmission unit, and a second toroidal cavity between input and output discs of a second unit. The first and second toroidal cavities are equal in size, coaxial with each other and axially spaced from each other. In this conventional example, the input discs of both units are mounted on a torque shaft, and drivingly connected with each other by the torque shaft. A loading cam mechanism for producing an axial thrust load in accordance with an input torque is provided at the side of the input disc of the first unit, and the thrust load is transmitted to the input disc of the second unit by an axially movable tension rod. The torque shaft is hollow, and the tension rod is arranged coaxially in the hollow torque shaft.
The dual cavity type toroidal transmission of this conventional example requires two separate coaxial shafts, the torque shaft and tension rod for transmission of torque and transmission of thust load. This conventional transmission design, therefore, increases the number of required component parts, requires an additional machining process for forming coaxial shafts, and complicates the assembly process with the result of cost increase.
A similar toroidal CVT is disclosed in Japanese Patent Provisional Publication No. 63-125852.